Miguel de Icaza put out a short blog post this Saturday that insists the developers be cautious about C++ for performance and memory reasons. Miguel wrote that when developing Moonlight they evaluated between the Antigrain and Cairo libraries for 2D drawing. Moonlight was Mono's project to implement Silverlight in the web browser on Linux and other platforms but the project has since largely been abandoned.
Mono developers found Cairo to be the "clear winner" but Miguel ended up admitting "we built Moonlight in C++ for all the wrong reasons" like better performance and memory usage, but those metrics didn't end up remaining true once Moonlight was complete.
Miguel ended his latest, infrequent blog post with "Not only were the reasons wrong [for going with C++ in Moonlight], it is not clear we got any performance benefit and it is clear that we did worse with memory usage. But that is a story for another time."